What about when people leave their chairs to go in the pool/lazy river or to the restroom? Its just DH and I who travel together and we spend 90% of the time in the chairs that we have placed our stuff on. The remaining 10% of the time, we are either in the pool/lazy river or using the restroom. Would you really expect us to remove our stuff and place it in a locker while we go in the pool or to the restroom? That's not practical. I agree there are people who abuse the chairs by leaving their stuff there and disappearing for hours, but if you're going to make it so those people can't save their chairs, then it has to be enforced across the board. And unfortunately there are scenarios where it doesn't make sense.
Have you been on a cruise or stayed at any other resort, particularly in a tropical destination (i.e. all inclusive resorts)? The chair saving situation is par for the course at these kinds of places. People get up at the crack of dawn and claim a chair with a book or flip flop so they have a place to consider home base while they do whatever they want the rest of the day. Its not fair to others, but it is what it is. I haven't found a resort or cruise ship that even tries to enforce anything the way Aulani does. Also, this issue is why reserving of daybeds and cabanas have become more commonplace at different resorts - its the only way to ensure you have reserved seats where you can come and go at your leisure, and without getting up at daybreak to get it. And the resort makes money on it, which is preferable to them over potentially ticking guests off when they remove their stuff from a chair.
The lockers are a fair idea. If not room key enabled, maybe fingerprint enabled like what they have at Universal. Or even just cubbies - I have seen cubbies available at other resorts (and even my gym!) where people feel comfortable leaving things like towels and cover-ups while they enjoy the lazy river or pool. Of course, it wouldn't be good to leave phones or other valuables in something like that.